Project Summary RNAs are important in numerous cellular processes that range from the regulation of gene expression to serving as the specificity determinants in innate defense mechanisms. Research in this will test the hypothesis that proteins can distinguish small variations in the structures of an RNA motif using proteome chips and biochemical and cell-based assays. This hypothesis will be examined with a well-defined simple RNA structure, the well-defined GNRA tetraloop and with the highly conserved portion in the 3'untranslated region (UTR) of the hepatitis C virus (HCV) genomic RNA. The two aims will: 1) Determine how changes in the structures of hairpin GNRA tetraloops will affect their specificity and affinity for target proteins. We will identify proteins from the yeast proteome chips that can specifically recognize the tetraloops, determine whether orthologs from E. coli proteome will have the similar specificities, measure the affinities and specificities of the RNA-protein interactions, and validate the interactions in vivo. 2) Identify the cellular proteins that could recognize the 3'UTR of the HCV genomic RNA. We will screen a protein chip that carries 3000 DNA/RNA binding proteins in humans and eleven proteins in HCV with the X region of the HCV 3'UTR. We will further confirm the candidate targets by in vivo pull down assays and determine whether they will affect HCV subgenomic replicon replication in cell-based assays. Anticipated results from Aim 1 will identify basic rules for protein-RNA interaction, but will likely reveal previously unknown functions of proteins. This information should provide the starting point for the future development of a protein-RNA interaction database. Anticipated results from Aim 2 will identify cellular proteins with high affinity to the HCV RNA that could influence viral infection. PUBLIC HEALTH RELEVANCE: Defining the rules for protein-RNA interaction will benefit many areas of biological science. We have successfully used proteome chips to identify nucleic acid-binding proteins that have novel activities in cells. We now seek to identify proteins that will bind a simple RNA motif, the GNRA tetraloop, and also the regulatory RNA motifs from the medically important hepatitis C virus. This two-year study will provide proof of principle and work out the technology needed for a more through study of the protein-RNA interactome and identify host factors that can influence the outcome of hepatitis C virus infection.